For preventing fire accident in high building, fireproof doors are widely installed between different floors. Generally, the locks of the fireproof doors are installed in the doorframes and have very complicated structures so that the manufacturing processes are tedious. Furthermore, the lock is difficult in operation and is easy to have faults. Especially, when the fireproof door is opened, a lower protruded head will protrude upwards due to a compression of a spring so that it will contact the groove with the movement of the door. Not only the ground is worn and the door will be destroyed. Furthermore, generally, the fireproof door is closed, when fire accident occurs.
In general design, in high temperature, the buckling studs will not reduce inwards and then the fireproof doors will not open automatically so as to prevent the expansion of fire. This is the main function of the fireproof door.